High molecular weight polymers as viscosity modifiers

ABSTRACT

A lubricating composition comprises a base oil and between 10 ppm and 1000 ppm by mass of a viscosity modifier, the viscosity modifier comprising a polymer having a number average molecular weight greater than 500,000. The polymer&#39;s side-chains may be branched or unbranched. The polymer is preferably selected from the group consisting of polyolefin, poly alpha olefin, poly internal olefin, ethylene-propylene copolymers, ethylene-propylene-diene copolymers, ethylene-propylene-acrylate copolymers, ethylene-propylene-methacrylate copolymers, ethylene-propylene-aromatic copolymers, ethylene-propylene-diene-acrylate copolymers, ethylene-propylene-diene-methacrylate copolymers, and combinations thereof.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/643,929, filed on 8 May 2012, which is incorporated herein byreference.

FIELD OF THE INVENTION

The invention relates to the use of ultra-high molecular weight polymersas viscosity modifiers and more particularly to the use of lowconcentrations of ultra-high molecular weight copolymers as viscositymodifiers in lubricating oils and similar compositions. The resultinglubricating oils are particularly advantageous in direct injectionengines.

BACKGROUND OF THE INVENTION

Conventional wide span lubricants contain polymers that serve asViscosity Index Improvers (VIIs), which are a necessary component ofwide-span multi-grade oils.

In conventional port injected engines, fuel washes the back on theintake valve and helps prevent the formation of deposits there. Even so,in conventional engines, polymer additives in the engine lubricating oilcontribute to engine deposits, which are in turn controlled with otheradditives.

In internal combustion engines, gasoline direct injection (GDI) is atype of fuel injection system that may be used in four-stroke engines.In contrast to conventional carburetor or port injection systems inwhich fuel is supplied upstream of the cylinder inlets, in a GDI system,the fuel is pressurized and injected directly into the combustionchamber of each cylinder. In modern engines the injection can be finelycontrolled so as to minimize heat loss and combustion inefficiency.Thus, the major advantages of a GDI engine are increased fuel efficiencyand higher power output.

In GDI engines, fuel does not wash the back on the intake valve. In GDIengines, cylinder intake valves can accumulate high levels of deposits,which tend to impair engine performance and reduce fuel economy.Viscosity modifiers present in the engine lubricating oil contribute tothe formation of these deposits by degrading on hot surfaces,particularly on the back of intake valves, creating deposits that canrestrict air flow into the combustion chamber, thereby reducing engineefficiency. Thus, it would be advantageous to greatly reduce the VIIconcentration in modern engine oils so as to reduce or prevent intakevalve deposits.

For narrow span oils like SAE 5W-20, this can be accomplished by usingsynthetic base oils, also referred to as gas to liquids (GTL),poly-alpha olefins (PAOs) base oils or other base stocks withsufficiently high viscosity index. When shifting to a wider span multigrade oil like SAE 0W-20 or wider oils, however, VIIs are stillrequired. Thus, it is desirable to provide an engine oil that has thedesired viscometric properties without including viscosity modifiers ata level that causes unacceptable levels of deposit formation.

SUMMARY OF THE INVENTION

In accordance with preferred embodiments of the invention there isprovided an engine oil that has desirable viscometric properties andgreatly reduced viscosity modifier (VM) treat levels, thus reducing thetendency of forming intake valve deposits which can reduce engineperformance, decreasing fuel economy and increasing carbon dioxideemissions.

According to certain embodiments, a composition for lubricating anengine according to the present invention comprises a base oil andbetween 10 ppm and 1000 ppm by mass of a viscosity modifier wherein theviscosity modifier is a polymer having a number average molecular weightgreater than 500,000.

The polymer preferably comprises long polymer strands. The polymer'sside-chains may be branched or unbranched. The polymers are linearmolecules having side chains that are shorter than the backbone. Thepolymers preferably are long-chained polymers with a backbone that is atleast ten times as long as the side-chains.

The polymer preferably comprises ethylene and propylene and morepreferably comprises at least 50 percent by weight ethylene andpropylene.

Additionally or alternatively, the polymer may comprise side-chains thateach comprises 1 to 30 carbon atoms.

The polymer is preferably selected from the group consisting of, but notlimited to, polyolefin, poly alpha olefin, poly internal olefin,ethylene-propylene copolymers, ethylene-propylene-diene copolymers,ethylene-propylene-acrylate copolymers, ethylene-propylene-methacrylatecopolymers, ethylene-propylene-aromatic copolymers,ethylene-propylene-diene-acrylate copolymers,ethylene-propylene-diene-methacrylate copolymers, and combinationsthereof.

Preferred polymers for use in the present compositions have numberaverage molecular weights greater than 1,000,000, more preferablygreater than about 2,000,000, even more preferably greater than about5,000,000. The concentration of the polymer in a composition accordingto the present invention preferably is between 10 ppm and 500 ppm bymass when used as the sole VM and/or it may be combined with other VMsknown to those skilled in the art.

A composition according to the present invention preferably has aviscosity index (VI) greater than 150, more preferably greater than 175,and still more preferably greater than 200. While inspecting theproperties of motor oils formulated with the ultra-high molecular weightpolymers we found that the viscosity index (VI) of the oils wassignificantly and unexpectedly high. VI values greater than 200 arenormally the result of using high treat rates of polymethacrylate VIimprovers; it was surprising to find VIs over 200 that were achievedusing low treat rates of the present hydrocarbon VI improvers.

When used as lubricants, the present compositions may also include atleast one additional component selected from the group consisting of butnot limited to additional viscosity modifiers, anti-wear additives,dispersants, detergents, pour point depressants, friction modifiers,corrosion inhibitors. anti-oxidants, and other additives such as areknown in the art.

In other embodiments, the present invention is used to formulate fuels,greases, transmission oils, hydraulic oils, gearbox oils, marine oils,and the like, and may in such formulations be combined with othersuitable additives.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

According to preferred embodiments of the invention, an effective enginelubricating oil can be provided by blending a base oil with at least oneultra-high molecular weight polymer. The polymer can be included in thebase oil at very low concentrations, or treat rates, with the resultthat deposits accumulate in an engine at a much lower rate than wouldotherwise occur.

The instant disclosure is a lubricant composition, and a method forreducing deposits in an engine. The instant disclosure also is the useof the lubricant composition as lubricant for an engine, as atransmission oil, or as a hydraulic oil.

In one embodiment, the instant disclosure provides a lubricantcomposition comprising a base oil and between 10 ppm and 1000 ppm bymass of a viscosity modifier, the viscosity modifier comprising at leastone polymer having a number average molecular weight greater than500,000.

Base Oil

Base oils suitable for use in the present invention include base oils asdescribed in API publication 1509, which includes Group I, Group II,Group III, Group IV, and Group V oils, and mixtures thereof, optionallyin combination with other base oils. API 1509 describes the base oilgroups and those skilled in the art can employ the current invention byusing those base oils with SAE J300, SAE J306, and other industrydocuments to create useful lubricating compositions. These engine oilswill have functional properties known to those skilled in the art suchthat they comply with SAE J300, API 1509, ILSAC GF-5, SAE D4485 andothers.

Polymer

The ultra-high molecular weight polymer or polymer blend may be presentat concentrations ranging from 10 ppm to 1000 ppm by mass, preferablyfrom 10 ppm to 500 ppm, and more preferably from 50 ppm to 250 ppm bymass. Concentrations in this range can be achieved by pre-blending thepolymer into a base oil concentrate, so that it can later be added tothe formulation as a liquid, by blending directly into the formulation,or by blending it into a solvent for delivery into the finalformulation.

Ultra-high molecular weight polymers suitable for use in the presentcompositions have number average molecular weights of at least 500,000.The composition comprises at least one such polymer.

The polymers preferably comprise long polymer strands. The polymer'sside-chains may be branched or unbranched. The polymers are linearmolecules having side chains that are shorter than the backbone. Thepolymers preferably are long-chained polymers with a backbone that is atleast ten times as long as the side-chains.

Preferably the ultra-high molecular weight polymers are formed fromblends comprising ethylene and propylene monomers.

Additionally or alternatively, the polymers may comprise side-chainsthat each comprises 1 to 30 carbon atoms.

In preferred embodiments, the composition comprises at least one polymerhaving a number average molecular weight of greater than 1,000,000, morepreferably greater than 2,000,000, more preferably greater than5,000,000.

Preferably, the composition comprises at least one polymer having anumber average molecular weight of greater than 500,000 and smaller than100,000,000, more preferably smaller than 75,000,000, even morepreferably smaller than 50,000,000, and most preferably smaller than30,000,000.

In one embodiment, the composition comprises at least one polymer havinga number average molecular weight of greater than 1,000,000, morepreferably greater than 2,000,000, and smaller than 100,000,000, morepreferably smaller than 75,000,000, even more preferably smaller than50,000,000.

The polymers preferably are long-chained polymers with a backbone thatis at least ten times as long as the side-chains, preferably at least 50times, even more preferably at least 100 times, still more preferably atleast 1000 times as long as the side-chains.

The polymers preferably are long-chained polymers with a length that isat least ten times the width, preferably at least 50 times, even morepreferably at least 100 times the width, still more preferably at least1000 times the width.

The polymers may comprise side-chains of different sizes, wherebypreferably at least 90% of the side-chains, preferably all side-chains,comprise 1 to 30 carbon atoms, preferably 6 to 16 carbon atoms.

The polymers may comprise side-chains whereby preferably at least 20% ofthe side-chains, preferably least 50% of the side-chains, have the samelength and comprise 1 to 30 carbon atoms, preferably 6 to 16 carbonatoms, more preferably 8 to 12 carbon atoms, even more preferably 8carbon atoms.

In one embodiment, the composition comprises at least one polymer havinga number average molecular weight of greater than 500,000, preferablygreater than 1,000,000, more preferably greater than 2,000,000, evenmore preferably greater than 5,000,000 and smaller than 20,000,000,preferably smaller than 15,000,000, more preferably smaller than10,000,000. Additionally or alternatively, the composition comprises atleast one polymer having a number average molecular weight of greaterthan 10,000,000, preferably greater than 15,000,000, more preferablygreater than 20,000,000 and smaller than 100,000,000, more preferablysmaller than 75,000,000, even more preferably smaller than 50,000,000,still more preferably smaller than 30,000,000.

The polymer is preferably an olefin copolymer selected from the groupconsisting of, but not limited to, polyolefin, poly alpha olefin, polyinternal olefin, ethylene-propylene copolymers, ethylene-propylene-dienecopolymers, ethylene-propylene-acrylate copolymers,ethylene-propylene-methacrylate copolymers, ethylene-propylene-aromaticcopolymers, ethylene-propylene-diene-acrylate copolymers,ethylene-propylene-diene-methacrylate copolymers, and combinationsthereof. One compound that is particularly preferred for use in theinvention is available from ConocoPhillips of Houston, Tex. under thename LP™ 100 Flow Improver. Other highly preferred compounds areavailable from FlowChem of Houston, Tex.

Also suitable for use are synthetic rubber compounds, nitro- andoxy-functionalized olefin copolymers, antioxidant-grafted copolymers,dispersant-grafted copolymers, and combinations thereof.

For additional specific polymer compositions that can be used in thepresent inventions and for methods of making them, reference is made toU.S. Pat. Nos. 4,693,321, 5,539,044, 5,376,697, 6,172,151, 6,399,676,6,576,732, 6,596,832, 6,765,053, 6,939,902, 7,285,582, 7,361,628,7,763,671, 7,888,407, and European Patent EP0196350, each of which isincorporated herein in its entirety.

In one embodiment, the inventive polymer preferably contains ethyleneand propylene in ratios normally seen in other E/P polymers consistingfrom about 10 to 70% ethylene and from about 20 to 90% propylene, withadditional monomer optionally included. Increasing the ethylene contentincreases thickening power but decreases solubility in certain basefluids. Thus the skilled practitioner will choose polymer compositionssuited to the specific use intended.

Other inventive polymers preferably are poly alpha olefins of decene,tetradecene, or combinations thereof. Poly alpha olefins of decene haveside-chains with 8 carbon atoms. Poly alpha olefins of tetradecene haveside-chains with 12 carbon atoms. Poly alpha olefins of decene andtetradecene have side-chains with 8 carbon atoms and side-chains with 12carbon atoms.

The use of additional monomers is also anticipated to allow theinventive polymer to have the properties of dispersants, antioxidants,pour point depressants and other additive chemistry known to thoseskilled in the art.

Additives

In addition to the ultra-high molecular weight polymers, variousadditives are known for use in lubricating compositions may be includedin the present lubricating composition. These include but are notlimited to detergents, dispersants, anti-wear agents, anti-oxidants,pour point depressants, corrosion inhibitors, friction modifiers,anti-foaming agents and additional viscosity modifiers, all of which areknown in the art, which may be added separately or in combination so asto enhance to lubricant formulations performance.

In some preferred embodiments a lubricating composition includes both anultra-high molecular weight polymer and a second viscosity modifierselected from the group consisting of those currently used by thoseskilled in the art, which include but are not limited to olefincopolymers (OCPs), E/P, EPDM, Styrene-isoprene, Styrene-butadiene,polyacrylates and polymethacrylates and others. If present, the secondviscosity modifier may be present in an amount ranging from 0.1 wt % to10 wt %. By way of example only, such additives include those disclosedU.S. Pat. Nos. 3,522,180; 4,026,809; 4,146,489; 4,340,689; and4,780,689, which are each incorporated herein by reference.

U.S. Pat. No. 3,522,180 discloses a method for the preparation of anethylene-propylene copolymer substrate effective as a viscosity indeximprover for lubricating oils. U.S. Pat. No. 4,026,809 discloses graftcopolymers of a methacrylate ester and an ethylene-propylene-alkylidenenorbornene terpolymer as a viscosity index improver for lubricatingoils. U.S. Pat. No. 4,146,489 discloses a graft copolymer where thepolymer backbone is an oil-soluble ethylene-propylene copolymer or anethylene-propylene-diene modified terpolymer with a graft monomer of 2-or 4-vinylpyridine or N-vinylpyrrolidone to provide a dispersant VIimprover for lubricating oils. U.S. Pat. No. 4,340,689 discloses aprocess for grafting a functional organic group onto anethylene-propylene copolymer or an ethylene-propylene-diene terpolymer.U.S. Pat. No. 4,780,228 discloses the grafting of a hydrocarbon polymerin the absence of a solvent in the presence of a free radical initiatorand a chain-terminating agent followed by a reaction with an amine,polyol or an aminoalcohol.

EXAMPLES

It has been discovered that inclusion of an ultra-high molecular weightpolymer in an engine oil can significantly increase the viscosity index,even at extremely low treat rates. For example, VI increases of 30points were observed in more than one instance, which was mostunexpected. Table 1 below gives some test results showing the surprisingimprovement in VI.

TABLE 1 Lubricating Oil Comp. Comp. Ex. 1 Ex. 2 Ex. 3 Ex. 4 KV40 (cSt)45.14 35.2 43.72 32.38 Kv100 (cSt) 9.72 7.348 8.513 6.371 VI 208 181 176152 CCS-35 (cP) 5580 5110 5590 5140

In table 1, KV40 and KV100 are the kinematic viscosity at 40° C. and100° C. respectively, and CCS-35 is the value measured in a coldcranking simulator at −35° C.

In Table 1, all Examples are based on a commercially available,additive-containing SAE 0W-20 lubricating oil. Examples 1 and 2consisted of the commercially available SAE 0W-20 oil plus 100 mass ppmof LP™ 100 Flow Improver from ConocoPhillips of Houston, Tex. In Example1, a commercially available lubricant was used as-sold. In Example 2, aviscosity modifier that was present in the commercial lubricant, namelya hydrogenated isoprene star polymer with a shear stability of between10 and 20 percent viscosity loss in the finished lubricant using theKurt Orbahn shear stability test, comprising 4.5 mass percent of thecommercial lubricant, was removed from the formulation. It was foundthat a stirring bar or paddle mixer is preferred over a high-shearblender for mixing the compositions, as the latter tends to reduce theviscosity of the final composition. In contrast, Comparative Examples 3and 4 contained no LP™ 100 Flow Improver. Otherwise, ComparativeExamples 3 and 4 consisted of the same lubricants as Examples 1 and 2,namely commercially available SAE 0W-20 oil with and without,respectively, 4.5 mass percent of the viscosity modifier describedabove.

Table 2 below gives other test results showing the surprisingimprovement in VI.

TABLE 2 Lubricating Oil Comp. Ex. 5 Ex. 6 KV40 (cSt) 44.52 43.58 Kv100(cSt) 9.60 8.51 VI 206 177 CCS-35 (cP) 5535 5539

In Table 2, both Examples are based on a commercially available,additive-containing SAE 0W-20 lubricating oil. Examples 5 consisted ofthe commercially available SAE 0W-20 oil plus 200 mass ppm of a polymerwith a molecular weight of about 25,000,000 and side-chains comprising 8carbon atoms. In Example 5, a commercially available lubricant was usedas-sold. Comparative Example 6 consisted of the same lubricant asExample 5, namely commercially available SAE 0W-20 oil.

The VI of 208 achieved by Example 1 and the VI of 206 achieved byExample 5 are unheard of in hydrocarbon systems that do not include PMAthickeners and may have strong fuel economy implications. In addition,it is expected that the use of a lubricant containing such a lowconcentration of polymer would lower the probability of the polymercoming into contact with the back of the intake valves, thereby reducingthe rate at which deposits will form. It is further noted that inExamples 1 and 5, addition of the flow improver increases the KV 100such that the oil shifts into the 0W-30 range; this can be adjusted inpractice.

It has further been discovered that inclusion of an ultra-high molecularweight polymer in a gear oil can significantly increase the viscosityindex. Table 3 below gives some transmission fluid test results.

TABLE 3 Transmission Fluid Comp. Ex. 7 Ex. 8 KV40 (cSt) 31.42 27.60Kv100 (cSt) 6.954 6.05 VI 192 176

In Table 3, the Examples are based on a commercially available SAE J306transmission fluid. Example 7 consisted of the commercially availabletransmission fluid plus 100 mass ppm of LP™ 100 Flow Improver fromConocoPhillips of Houston, Tex. Comparative Example 8 consisted of thecommercially available transmission fluid with no added flow improver.As can be seen, the viscosity index of the transmission fluid went from176 to 192.

Table 4 below gives gear oil test results.

TABLE 4 Gear oil Comp. Comp. Ex. 9 Ex. 10 Ex. 11 Ex. 12 KV40 (cSt) 11.3812.44 13.11 12.44 Kv100 (cSt) 3.36 3.18 3.3 3.13 VI 186 122 124 114

In Table 4, the Examples are based on a gear oil. Example 9 consisted ofa gear oil with a traditional viscosity modifier plus 100 mass ppm of apolymer with a molecular weight of about 25,000,000 and side-chainscomprising 8 carbon atoms. Comparative Example 10 consisted of the gearoil with a traditional viscosity modifier with no added flow improver.As can be seen, the viscosity index of the gear oil with a traditionalviscosity modifier went from 122 to 186 by adding 100 mass ppm of thepolymer.

Example 11 consisted of a gear oil without a viscosity modifier plus 100mass ppm of a polymer with a molecular weight of about 25,000,000 andside-chains comprising 8 carbon atoms. Comparative Example 12 consistedof the gear oil without a viscosity modifier with no added flowimprover. As can be seen, the viscosity index of the gear oil without aviscosity modifier went from 114 to 124 by adding 100 mass ppm of thepolymer.

It is expected that compositions according to the present claims willhelp increase efficiency and those reduce fuel consumption when used tolubricate internal combustion engines and in particular gasoline directinjection engines. It is further expected that the compositionsaccording to the present invention will provide other advantages whenused in other applications, including as transmission oils, hydraulicoils, gearbox oils, and/or marine oils.

What is claimed is:
 1. A lubricant composition, comprising: a base oil;between 10 ppm and 1000 ppm by mass of a viscosity modifier, theviscosity modifier comprising at least one polymer having a numberaverage molecular weight greater than 500,000.
 2. The compositionaccording to claim 1 wherein the polymer has side-chains that may bebranched or unbranched, and wherein the polymer has a backbone that isat least ten times as long as the side-chains.
 3. The compositionaccording to claim 1 wherein the polymer comprises side-chains ofdifferent sizes, whereby at least 90% of the side-chains comprise 1 to30 carbon atoms.
 4. The composition according to claim 1 wherein thepolymer comprises side-chains whereby at least 20% of the side-chainshave the same length and comprise 1 to 30 carbon atoms.
 5. Thecomposition according to claim 1 wherein the polymer has a numberaverage molecular weight greater than 1,000,000.
 6. The compositionaccording to claim 1 wherein the polymer has a number average molecularweight smaller than 100,000,000.
 7. The composition according to anyclaim 1 wherein the polymer has a number average molecular weight ofgreater than 500,000.
 8. The composition according to any claim 1wherein the concentration of the polymer in the composition is between10 ppm and 500 ppm by mass.
 9. The composition according to any claim 1wherein the polymer comprises ethylene and propylene.
 10. Thecomposition according to claim 9 wherein the polymer is selected fromthe group consisting of ethylene-propylene copolymers,ethylene-propylene-diene copolymers, ethylene-propylene-acrylatecopolymers, ethylene-propylene-methacrylate copolymers,ethylene-propylene-aromatic copolymers,ethylene-propylene-diene-acrylate copolymers,ethylene-propylene-diene-methacrylate copolymers, and combinationsthereof.
 11. The composition according to any claim 1 wherein at least50 weight percent of the polymer comprises ethylene and propylene. 12.The composition according to any claim 1 wherein the polymer comprisespolyolefin and/or poly alpha olefin and/or poly internal olefin.
 13. Thecomposition according to claim 12 wherein at least 50 weight percent ofthe polymer comprises polyolefin and/or poly alpha olefin and/or polyinternal olefin.
 14. The composition according to any claim 1 whereinthe composition has a viscosity index greater than
 150. 15. Thecomposition according to any claim 1 wherein the composition has aviscosity index greater than
 175. 16. The composition according to anyclaim 1 wherein the composition further includes at least one additionalcomponent selected from the group consisting of additional viscositymodifiers, anti-wear additives, dispersants, detergents, pour pointdepressants, corrosion inhibitors, anti-oxidants, combustion enhancers,and anti-foam agents.
 17. The use of a composition according to claim 1as a lubricant for an engine.
 18. The use of a composition according toclaim 1 as a transmission oil.
 19. The use of a composition according toclaim 1 as a hydraulic oil.
 20. A method for reducing deposits in anengine comprising using a composition according to claim 1 as alubricant.